Multiple-layer non-volatile memory devices, memory systems employing such devices, and methods of fabrication thereof

ABSTRACT

In multiple-layered memory devices, memory systems employing the same, and methods of forming such devices, a second memory device layer on a first memory device layer comprises a second substrate including a second memory cell region. The second substrate includes only a single well in the second memory cell region, the single well of the second memory cell region comprising a semiconducting material doped with impurity of one of a first type and second type. The single well defines an active region in the second memory cell region of the second substrate. Multiple second cell strings are arranged on the second substrate in the second active region. Although the second memory cell region includes only a single well, during a programming or erase operation of the memory cells of the second layer, requiring a high voltage to be applied to the single well in the substrate of the second layer, the high voltage will not interfere with the operation of the peripheral transistors of the first layer, second layer, or other layers, since they are isolated from each other. As a result, the substrate of the second layer can be prepared to have a thinner profile, and with fewer processing steps, resulting in devices with higher-density, greater reliability, and reduced fabrication costs.

RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 12/456,391, filed on Jun. 16, 2009, which claims the benefit ofKorean Patent Application No. 10-2008-0058511, filed on Jun. 20, 2008,the contents of which are incorporated herein by reference in theirentirety.

BACKGROUND

With the continued emphasis on highly integrated electronic devices,there is an ongoing need for semiconductor memory devices that operateat higher speeds and lower power and that have increased device density.To accomplish this, devices with aggressive scaling and multiple-layereddevices with transistor cells arranged in horizontal and vertical arrayshave been under development.

In one approach, planar memory cells, for example NAND memory cells, areformed in a conventional horizontal, or planar, array. Multiplehorizontal arrays are then stacked in a vertical direction, resulting ina three-dimensional device configuration.

In the conventional planar NAND memory configuration, memory cells arearranged in a high-density array in a memory cell region of the device,and peripheral transistors of relatively lower density are arranged in aperipheral region of the device. The memory cells and peripheraltransistors are arranged on the device substrate in regions of thesubstrate referred to as wells, which are regions that are doped with aparticular type of impurity.

In the memory cell region, the memory cells are positioned on thesubstrate in a pocket well that surrounds the memory cells; the pocketwell is in turn positioned in a deep well. In an example where thesubstrate is a p-type substrate, the deep well can be n-type, and thepocket well can be p-type. At the same time, in the peripheral circuitregion, the peripheral transistors are positioned on the substrate in aperipheral well, which can be n-type or p-type. Combining the pocketwell and deep well in the memory cell region and the peripheral well inthe peripheral region, such a well configuration is referred to as a“triple well” configuration.

During a program or erase operation of a non-volatile memory device, ahigh voltage is typically applied to the pocket well in the memory cellregion of the device. The peripheral region must therefore be isolatedfrom the memory cell region during this operation in order to avoidinterference with the peripheral region during the program or eraseoperation, since the memory region and peripheral region share a commonsubstrate. The presence of the deep well in the memory cell regionprovides this isolation function.

With the desire for increased density in electronic devices, formationof multiple-layered devices continues to become more attractive tosemiconductor manufacturers. However, the need for a deep well in thememory cell region of each layer can increase manufacturing costs andcan limit device density in the vertical direction of a multiple-layereddevice.

SUMMARY

Embodiments of the present invention are directed to multiple-layeredsemiconductor devices, memory systems employing such devices, andmethods of forming semiconductor devices having multiple layers wherebythe upper layers of the multiple-layered device comprise a memory cellregion including only a single well. As a result, the devices can beformed to have increased vertical density, and can be formed moreefficiently by reducing the number of manufacturing steps required forproducing the upper layers. This results in a more-efficient fabricationprocess that is more economical for production of the end-devices.

In one aspect, a multiple-layered memory device, comprises: a firstmemory device layer comprising: a first substrate including a firstmemory cell region, the first memory cell region including a first wellpositioned in an upper region thereof and a second well positioned inthe first well, the first substrate comprising a semiconducting materialdoped with impurity of a first type, the first well comprising asemiconducting material doped with impurity of a second type oppositethe first type, and the second well comprising a semiconducting materialdoped with impurity of the first type, a first active region of thefirst substrate being defined by the second well; and multiple firstcell strings arranged on the first substrate in the first active region;and a second memory device layer on the first memory device layercomprising: a second substrate including a second memory cell region,the second substrate including only a single well in the second memorycell region, the single well of the second memory cell region comprisinga semiconducting material doped with impurity of one of the first typeand second type, the single well defining a second active region in thesecond memory cell region of the second substrate; and multiple secondcell strings arranged on the second substrate in the second activeregion.

In one embodiment, the first type of impurity is n-type and the secondtype of impurity is p-type.

In another embodiment, the first type of impurity is p-type and thesecond type of impurity is n-type.

In another embodiment, the semiconducting material of the single well ofthe second substrate is doped with impurity of the first type.

In another embodiment, at least one of the first and second memorydevice layers further includes a peripheral region.

In another embodiment, the first memory device layer further includes afirst peripheral region including first peripheral transistors.

In another embodiment, the second memory device layer further includes asecond peripheral region including second peripheral transistors.

In another embodiment, the second peripheral region of the second memorydevice layer is physically isolated from the second cell strings of thesecond active region.

In another aspect, a method of forming a multiple-layered memory devicecomprises: providing a first memory device layer comprising: providing afirst substrate including a first memory cell region, the firstsubstrate comprising a semiconducting material doped with impurity of afirst type; providing a first well in an upper region of the firstmemory cell region, the first well comprising a semiconducting materialdoped with impurity of a second type opposite the first type; andproviding a second well in the first well, the second well comprising asemiconducting material doped with impurity of the first type, thesecond well of defining a first active region of the first substrate;and providing multiple first cell strings arranged on the firstsubstrate in the first active region; and providing a second memorydevice layer on the first memory device layer comprising: providing asecond substrate including a second memory cell region, the secondsubstrate including only a single well in the second memory cell region,the single well of the second memory cell region comprising asemiconducting material doped with impurity of one of the first type andsecond type, the single well defining a second active region in thesecond memory cell region of the second substrate; and providingmultiple second cell strings arranged on the second substrate in thesecond active region.

In one embodiment, the method further comprises providing an interlayerdielectric layer on the first memory device layer between the firstmemory device layer and the second memory device layer.

In another embodiment, the first type of impurity is n-type and thesecond type of impurity is p-type.

In another embodiment, the first type of impurity is p-type and thesecond type of impurity is n-type.

In another embodiment, the semiconducting material of the single well ofthe second substrate is doped with impurity of the first type.

In another embodiment, at least one of the first and second memorydevice layers further includes a peripheral region.

In another embodiment, providing the first memory device layer furthercomprises providing a first peripheral region including first peripheraltransistors on the first substrate.

In another embodiment, the method further comprises removing a portionof the second substrate that lies on the first peripheral region of thefirst substrate.

In another embodiment, the second substrate of the second memory devicelayer is constructed and arranged so that when the second substrate isprovided on the first substrate, no portion of the second substrate lieson the first peripheral region of the first substrate.

In another embodiment, providing the second memory device layer furthercomprises providing a second peripheral region including secondperipheral transistors on the second substrate.

In another embodiment, the method further comprises physically isolatinga portion of the second substrate of the second peripheral region of thesecond memory device layer from a portion of the second substrate of thesecond memory cell region, including the second cell strings.

In another aspect, a memory system comprises: a memory controller thatgenerates command and address signals; and a memory module comprising aplurality of memory devices, the memory module receiving the command andaddress signals and in response storing and retrieving data to and fromat least one of the memory devices. Each memory device is amultiple-layered memory device comprising: a plurality of addressablememory cells; a decoder that receives an address from an externalsource, and that generates a row signal and a column signal foraccessing at least one of the addressable memory cells duringprogramming and read operations; a first memory device layer comprising:a first substrate including a first memory cell region, the first memorycell region including a first well positioned in an upper region thereofand a second well positioned in the first well, the first substratecomprising a semiconducting material doped with impurity of a firsttype, the first well comprising a semiconducting material doped withimpurity of a second type opposite the first type, and the second wellcomprising a semiconducting material doped with impurity of the firsttype, a first active region of the first substrate being defined by thesecond well; and multiple first cell strings of the addressable memorycells arranged on the first substrate in the first active region; and asecond memory device layer on the first memory device layer comprising:a second substrate including a second memory cell region, the secondsubstrate including only a single well in the second memory cell region,the single well of the second memory cell region comprising asemiconducting material doped with impurity of one of the first type andsecond type, the single well defining a second active region in thesecond memory cell region of the second substrate; and multiple secondcell strings of the addressable cell strings arranged on the secondsubstrate in the second active region.

In one embodiment, the first type of impurity is n-type and the secondtype of impurity is p-type.

In another embodiment, the first type of impurity is p-type and thesecond type of impurity is n-type.

In another embodiment, the semiconducting material of the single well ofthe second substrate is doped with impurity of the first type.

In another embodiment, at least one of the first and second memorydevice layers further includes a peripheral region.

In another embodiment, the first memory device layer further includes afirst peripheral region including first peripheral transistors.

In another embodiment, the second memory device layer further includes asecond peripheral region including second peripheral transistors.

In another embodiment, the second peripheral region of the second memorydevice layer is physically isolated from the second cell strings of thesecond active region.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of theembodiments of the invention will be apparent from the more particulardescription of embodiments of the invention, as illustrated in theaccompanying drawings in which like reference characters refer to thesame parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention. In the drawings:

FIG. 1A is a plan view of a first semiconductor layer of a semiconductordevice including a cell array region and a peripheral region, inaccordance with an embodiment of the present invention. FIG. 1B is aplan view of a second semiconductor layer of a semiconductor deviceincluding a cell array region and a peripheral region, in accordancewith an embodiment of the present invention.

FIGS. 2A-2F are cross-sectional diagrams, taken along section lines I-I′of FIGS. 1A and 1B, of a process for forming a multiple-layeredsemiconductor device in accordance with an embodiment of the presentinvention.

FIG. 3 is a plan view of a second semiconductor layer of a semiconductordevice including a cell array region and a peripheral region, inaccordance with another embodiment of the present invention.

FIGS. 4A and 4B are cross-sectional diagrams, taken along section linesI-I′ of FIGS. 1A and 3 respectively, of a process for forming amultiple-layered semiconductor device in accordance with anotherembodiment of the present invention.

FIGS. 5A-5C are cross-sectional diagrams of a process for forming asemiconductor device in accordance with another embodiment of thepresent invention.

FIG. 6 is a block diagram of a memory card that includes a semiconductordevice in accordance with the embodiments of the present invention.

FIG. 7 is a block diagram of a memory system that employs a memorymodule including semiconductor devices in accordance with theembodiments of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will now be described more fullyhereinafter with reference to the accompanying drawings, in whichpreferred embodiments of the invention are shown. This invention may,however, be embodied in different forms and should not be construed aslimited to the embodiments set forth herein. Like numbers refer to likeelements throughout the specification.

It will be understood that, although the terms first, second, etc. areused herein to describe various elements, these elements should not belimited by these terms. These terms are used to distinguish one elementfrom another. For example, a first element could be termed a secondelement, and, similarly, a second element could be termed a firstelement, without departing from the scope of the present invention. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items.

It will be understood that when an element is referred to as being “on”or “connected” or “coupled” to another element, it can be directly on orabove, or connected or coupled to, the other element or interveningelements can be present. In contrast, when an element is referred to asbeing “directly on” or “directly connected” or “directly coupled” toanother element, there are no intervening elements present. Other wordsused to describe the relationship between elements should be interpretedin a like fashion (e.g., “between” versus “directly between,” “adjacent”versus “directly adjacent,” etc.). When an element is referred to hereinas being “over” another element, it can be over or under the otherelement, and either directly coupled to the other element, orintervening elements may be present, or the elements may be spaced apartby a void or gap.

The terminology used herein is for the purpose of describing particularembodiments and is not intended to be limiting of the invention. As usedherein, the singular forms “a,” “an” and “the” are intended to includethe plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises,”“comprising,” “includes” and/or “including,” when used herein, specifythe presence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

FIG. 1A is a plan view of a first semiconductor layer of a semiconductordevice including a cell array region and a peripheral region, inaccordance with an embodiment of the present invention. FIG. 1B is aplan view of a second semiconductor layer of a semiconductor deviceincluding a cell array region and a peripheral region, in accordancewith an embodiment of the present invention. FIGS. 2A-2F arecross-sectional diagrams, taken along section lines I-I′ of FIGS. 1A and1B, of a process for forming a multiple-layered semiconductor device inaccordance with an embodiment of the present invention.

Referring to FIG. 2A, a first layer 110 of a semiconductor deviceincludes a memory cell region 104 and a peripheral region 106 formed ina substrate 100. The memory cell region 104 includes a plurality ofmemory cells, in this case arranged in cell strings 120. Each cellstring 120 includes a plurality of memory cell transistors 126, a groundselection transistor 122 and a string selection transistor 124 arrangedin a horizontal configuration. First impurity-doped regions 132 areprovided in the substrate 100 between neighboring transistors 122, 124,126 and second and third impurity-doped regions 130, 134 are provided inthe substrate 100 between neighboring cell strings 120. The peripheralregion 106 includes a plurality of peripheral transistors 140. Fourthimpurity-doped regions 142 are positioned at sidewalls of the peripheraltransistors 140. An insulative capping layer 151 is provided over theresulting structure in the memory cell region 104 and in the peripheralregion 106. A first interlayer dielectric layer 150 is provided over thecapping layer 151.

In the memory cell region 104, the cell strings 120 are positioned onthe substrate 100 in a pocket well 116 that surrounds the memory cells.The pocket well 116 is in turn positioned in a deep well 114. In anexample where the substrate 100 is a p-type substrate, the deep well 114can be n-type, and the pocket well can be p-type. In the peripheralcircuit region 106, the peripheral transistors 140 are positioned on thesubstrate 100 in a peripheral well 118, which can be n-type or p-type.Combining the pocket well 116 and deep well 114 in the memory cellregion 104 and the peripheral well 118 in the peripheral region, such awell configuration 114, 116, 118 is referred to as a “triple well”configuration. The wells 114, 116, 118 are typically formed duringpreparation of the substrate 100, prior to fabrication of the varioustransistors in the memory cell region 104 and peripheral region; howeverembodiments of the invention are not limited thereto, and well formationcan take place at another time during device fabrication.

Referring to FIG. 1A, it can be seen that in the memory cell region 104of the first layer 110, the memory cell region 104 is located on thesubstrate 100 so as to be surrounded by the pocket well 116, which, inturn is surrounded by the deep well 114. In another embodiment, notshown in the drawings, a plurality of pocket well regions 116corresponding to different cell strings 120 of the memory cell region104 can be formed in the memory cell region 104, and the plurality ofpocket well regions 116 can in turn be surrounded by the deep well 114.

Referring to FIG. 2B, a preliminary second layer 115A of a semiconductordevice is prepared to include a memory cell region 104A and a peripheralregion 106A formed in a substrate 160. The memory cell region 104Aincludes a plurality of memory cells, in this case arranged in cellstrings 170. Like the first layer 110, each cell string 170 of thepreliminary second layer 115A includes a plurality of memory celltransistors 176, a ground selection transistor 172 and a stringselection transistor 174 arranged in a horizontal configuration. Firstimpurity-doped regions 182 are provided in the substrate 160 betweenneighboring transistors 172, 174, 176 and second and thirdimpurity-doped regions 180, 184 are provided in the substrate 160between neighboring cell strings 170. The peripheral region 106A, inthis embodiment, does not include any peripheral transistors, oralternatively can include dummy transistors that are dormant orotherwise unused or unnecessary to device operation. An insulativesecond capping layer 181 is provided over the resulting structure in thememory cell region 104A and in the peripheral region 106A. The substrate160 of the preliminary second layer 115A is isolated from elements ofthe underlying first layer 110 by the first interlayer dielectric layer150. In the embodiment shown, the memory cell region 104A of thepreliminary second layer 115A is generally aligned with the memory cellregion 104 of the first layer 110. The peripheral region 106A of thepreliminary second layer 115A at this time covers the peripheral region106 of the first layer.

In the memory cell region 104A of the preliminary second layer 115A, thecell strings 170 are positioned on the substrate 160 in a single well119 that defines an active region of the preliminary second layer 115A.The substrate 160 of the preliminary second layer 115A can be formed,for example, of an SOI-type substrate, formed, for example, usingselective epitaxial growth (SEG) or laser-induced epitaxial growth(LEG), or otherwise can be applied using a wafer-bonding process. In anexample where the material of the substrate 160 is n-type, the singlewell 119 can be p-type. The SOI-type substrate can include, for example,the substrate 160, formed of silicon, and positioned on the underlyinginsulating layer 150. In an example embodiment for forming the singlewell 119, the single well 119 can be formed by applying a dopant to anupper region of the substrate 160 surface, and the dopant is thendiffused into the body of the substrate 160 using a high-temperatureapplication. As a result, the highest concentration of impurities is ata bottom portion of the single well 119. In this embodiment, the singlewell 119 can optionally also be provided in the peripheral region 106Aof the preliminary second layer 115A, in order to simplify processing ofthe substrate 160 of the preliminary second layer 115A during itspreparation.

Referring to FIG. 2C, the peripheral region 106A of the substrate 160 ofthe second layer 115A is removed. Also removed is the portion 181A ofthe second capping layer 181 in the peripheral region 106A. In thismanner, the resulting second layer 115 includes only the memory cellregion 104A, and does not include the removed portion 164 of thesubstrate 160 that lies in the peripheral region 106A of the device. Invarious embodiments, the portion 181A of the second capping layer 181and the portion 164 of the substrate 160 can be removed usingapplication of a hard mask layer, followed by an etch of the portions tobe removed.

Referring to FIG. 1B, it can be seen that the second layer 115 of thesemiconductor device includes the memory cell region 162, and does notinclude removed portions 164 of the peripheral region 106A, and removedportions 166 of other neighboring regions surrounding the memory cellregion 162.

Referring to FIG. 2D, contacts for common source lines (CSL) are formed.A second interlayer dielectric layer 190 is provided over the secondcapping layer 181. First contact holes 191 are formed in the second andfirst layers 115, 110 of the resulting structure to contact theunderlying source regions 130 of the cell strings 120 of the first layer110. The first contact holes 191 are formed so as to be isolated fromother elements of the first and second layers 110, 115. Similarly,second contact holes 193 are formed in the second layer 115 of theresulting structure to contact the underlying source regions 180 of thecell strings 120 of the second layer 115. The second contact holes 193are formed so as to be isolated from other elements of the second layer115. The first and second contact holes 191, 193 are then filled with aconductive material to form CSL contacts 192, 194, that provideelectrical contact with the source regions 130, 180.

Referring to FIG. 2E, contacts for bit lines are formed. A thirdinterlayer dielectric layer 195 is provided over the resultingstructure. First bit line holes 196 are formed in the second and firstlayers 115, 110 of the resulting structure to contact the underlyingcommon drain regions 134 of the cell strings 120 of the first layer 110.The first bit line holes 196 are formed so as to be isolated from otherelements of the first and second layers 110, 115. Similarly, second bitline holes 198 are formed in the second layer 115 of the resultingstructure to contact the underlying common drain regions 184 of the cellstrings 120 of the second layer 115. The second bit line holes 198 areformed so as to be isolated from other elements of the second layer 115.The first and second bit line holes 196, 198 are then filled with aconductive material for providing bit line plugs 197, 199 that provideelectrical contact with the common drain regions 134, 184. At this time,peripheral transistor contact holes 200 can also be formed through thethird, second and first interlayer dielectric layers 195, 190, 150 inthe peripheral region of the device, and plugs applied to formperipheral contacts 210 that contact the source, drain and/or gateelements 140, 142 of the peripheral transistors of the first layer 110.

Referring to FIG. 2F, bit lines are formed. Bit lines 220 are foamed andpatterned on the resulting structure to connect the common drain regions134, 184 of the cell strings 120, 170 of the first and/or second layers110, 115 of the device. At the same time, other interconnect vias 222can be formed in the peripheral region 106A and in the memory cellregion 104A. A fourth interlayer dielectric layer 230 is optionallyprovided over the resulting structure to insulate the bit lines 220 andinterconnect vias 222.

In the resulting multiple-layered semiconductor device, the substrate160 of the second layer 115 is physically and electrically isolated fromthe peripheral transistors 140 of the first layer 110 by virtue of thefact that they lie on different substrates. As a result, the operationof the cell strings 170 of the second layer 115 is isolated from theperipheral transistors 140 of the first layer 110. Thus, during aprogramming or erase operation of the memory cells 176 of the secondlayer 115, requiring a high voltage to be applied to the single well 119in the substrate 160 of the second layer 115, the high voltage will notinterfere with the operation of the peripheral transistors 140 of thefirst layer 110, since they are physically and electrically isolatedfrom each other. Therefore, a multiple well configuration is notrequired in the second layer 115. As a result, the substrate 160 of thesecond layer 115 can be prepared to have a thinner profile, and withfewer processing steps, resulting in devices with higher density,greater reliability, and reduced fabrication costs.

At the same time, since the memory cells 126 of the first layer 110 areformed in the multiple-well structure of the memory cell region 104A ofthe first substrate 100, including the pocket well 116 and deep well114, and since the peripheral transistors 140 of the first layer areformed in the peripheral well 118 of the peripheral region 106A of thefirst substrate 100, they too are isolated from each other, as a resultof the triple-well configuration of the first layer 110. Therefore,during a programming or erase operation of the memory cells 126 of thefirst layer 110, requiring a high voltage to be applied to the pocketwell 116, the high voltage will not interfere with the operation of theperipheral transistors 140 in the peripheral region 106A of the firstlayer 110, since they are isolated from each other.

FIG. 3 is a plan view of a second semiconductor layer of a semiconductordevice including a cell array region and a peripheral region, inaccordance with another embodiment of the present invention. FIGS. 4Aand 4B are cross-sectional diagrams, taken along section lines I-I′ ofFIGS. 1A and 3 respectively, of a process for forming a multiple-layeredsemiconductor device in accordance with another embodiment of thepresent invention.

Referring to FIG. 4A, a first layer of a semiconductor device isprepared, for example in accordance with the first layer 110 describedabove in connection with FIG. 2A.

A second layer 117 of a semiconductor device is prepared to include amemory cell region 104A and a peripheral region 106A formed in asubstrate 165. The memory cell region 104A includes a plurality ofmemory cells, in this case arranged in cell strings 170. Like the firstlayer 110, each cell string 170 of the second layer 117 includes aplurality of memory cell transistors 176, a ground selection transistor172 and a string selection transistor 174 arranged in a horizontalconfiguration, as shown in FIG. 2B above. First impurity-doped regions182 are provided in the substrate 165 between neighboring transistorsand second and third impurity-doped regions 180, 184 are provided in thesubstrate 165 between neighboring cell strings 170. The peripheralregion 106A, in this embodiment, includes peripheral transistors 240,and source/drain regions 242 formed at sides of the gates of theperipheral transistors 240. Alternatively, the peripheral region 106Acan include dummy transistors that are dormant or otherwise unused orunnecessary to device operation, or can be void of peripheral or dummytransistors. An insulative second capping layer 181 is provided over theresulting structure in the memory cell region 104A and in the peripheralregion 106A. As in the above embodiment of FIGS. 1A-1B and 2A-2F, thesubstrate 165 of the second layer 117 is isolated from elements of theunderlying first layer 110 by the first interlayer dielectric layer 150.Also, as above, in the embodiment shown, the memory cell region 104A ofthe second layer 117 is generally aligned with the memory cell region104 of the first layer 110. The peripheral region 106A of the secondlayer 117 covers the peripheral region 106 of the first layer 110.

In the memory cell region 104A of the second layer 117, the cell strings170 are positioned on the substrate 165 in a single well 119 thatdefines an active region of the second layer 117. The substrate 165 ofthe second layer 117 can be formed, for example, of an SOI-typesubstrate, formed, for example, using selective epitaxial growth (SEG)or laser-induced epitaxial growth (LEG), or otherwise can be appliedusing a wafer-bonding process. In an example where the semiconductormaterial of the substrate 165 is n-type, the single well 119 can bep-type. In an example embodiment for forming the single well 119, thesingle well 119 can be formed by applying a dopant to an upper region ofthe substrate 165 surface, and the dopant is then diffused into the bodyof the substrate 165 using a high-temperature application. As a result,the highest concentration of impurities is at a bottom portion of thesingle well 119. In this embodiment, the single well 119 can optionallyalso be provided in the peripheral region 106A of the second layer 117,in order to simplify processing of the substrate 160 of the second layer117 during its preparation.

Continuing to refer to FIG. 4A, in this embodiment, a portion 166 of thesubstrate 165 of the second layer 117 is removed so that the peripheralregion 106A of the substrate 165 of the second layer 117 at a positionwhere the peripheral region 106A borders the memory cell region 104A, isphysically isolated, or spaced apart from, the memory cell region 104Aof the substrate 165 of the second layer 117. Such removal of theportion 166 can be accomplished, for example, by etching, such as dryetching, or laser ablation,

Referring to FIG. 3, it can be seen that the second layer 117 of thesemiconductor device includes the memory cell region 162 and theperipheral region 106A. It can also be seen that portions 166 betweenthe memory cell region 162 and the peripheral region 106A, and portionsbordering the memory cell region 162 are removed to provide the physicalisolation.

Referring to FIG. 4B, the resulting semiconductor device is processed inaccordance with the steps described above in connection with FIGS.2D-2F, for example to provide the common source line and bit lineconnectivity, as well as connectivity to the peripheral transistors.However, in the present embodiment shown in FIG. 4B, the peripheralregion 106A of the second layer 117 remains, and is not removed.Therefore, the peripheral transistors 240 of the second layer 117 areutilized in the resulting semiconductor device, instead of, or inaddition to, the peripheral transistors 140 of the first layer 110. Inthis embodiment, the applied second interlayer dielectric layer 190operates to fill the void in the second substrate 165 between the memorycell region 104A and the peripheral region 106A, thereby providingelectrical isolation between the two regions 104A, 106A of the secondsubstrate 165.

As a result of the isolation between the first and second layers 110,117, the substrate 165 of the memory cell region 104A of the secondlayer 117 is isolated from the peripheral transistors 140 of the firstlayer 110 by virtue of the fact that they lie on different substrates.In addition, in this embodiment, the substrate 165 of the memory cellregion 104A of the second layer 117 is isolated from the substrate 165of the peripheral transistors 240 of the second layer 117 by virtue ofthe fact that they are physically isolated from each other due to theremoved portion 166.

Accordingly, the operation of the cell strings 170 of the second layer117 is physically and electrically isolated from the peripheraltransistors 140 of the first layer 110. Also, in this embodiment, theoperation of the cell strings 170 of the second layer 117 is physicallyand electrically isolated from the peripheral transistors 240 of thesecond layer 110. Thus, during a programming or erase operation of thememory cells 176 of the second layer 117, requiring a high voltage to beapplied to the single well 119 in the substrate 165 of the second layer117, the high voltage will not interfere with the operation of theperipheral transistors 140 of the first layer 110, since they areisolated from each other. Nor will the application of the high voltageinterfere with the operation of the peripheral transistors 240 of thesecond layer 117, since they are isolated from each other. Therefore, amultiple well configuration is not required in the second layer 117. Asa result, the substrate of the second layer 117 can be prepared to havea thinner profile, and with fewer processing steps, resulting in deviceswith higher density, greater reliability, and reduced fabrication costs.

At the same time, since the memory cells 126 of the first layer 110 areformed in the multiple-well structure of the memory cell region 104A ofthe first substrate 100, including the pocket well 116 and deep well114, and since the peripheral transistors 140 of the first layer 110 areformed in the peripheral well 118 of the peripheral region 106A of thefirst substrate 100, they too are isolated from each other, as a resultof the triple-well configuration of the first layer 110. Therefore,during a programming or erase operation of the memory cells 126 of thefirst layer 110, requiring a high voltage to be applied to the pocketwell 116, the high voltage will not interfere with the operation of theperipheral transistors 140 in the peripheral region 106A of the firstlayer 110, since they are isolated from each other. Nor will theapplication of the high voltage to the memory cells 126 of the firstlayer 110 interfere with the operation of the peripheral transistors 240of the second layer 117, since they are isolated from each other.

FIGS. 5A-5C are cross-sectional diagrams of a process for forming asemiconductor device in accordance with another embodiment of thepresent invention.

Referring to FIG. 5A, a first layer of a semiconductor device isprepared, for example in accordance with the first layer 110 describedabove in connection with FIG. 2A.

In the present embodiment of FIGS. 5A-5C, a second layer 115 of asemiconductor device is prepared to include a memory cell region 104Aformed in a substrate 165A. The substrate 165A of the second layer 115does not include a peripheral region 106A in this embodiment. In otherwords, at the time when the second layer 115 is aligned and positionedon the first layer 110, no peripheral region 106A of the substrate 165Aof the second layer 115 is present in this embodiment. The memory cellregion 104A includes a plurality of memory cells, in this case arrangedin cell strings 170. Like the first layer 110, each cell string 170 ofthe second layer 115 includes a plurality of memory cell transistors176, a ground selection transistor 172 and a string selection transistor174 arranged in a horizontal configuration, as shown in FIG. 2B above.First impurity-doped regions 182 are provided in the substrate 165Abetween neighboring transistors and second and third impurity-dopedregions 180, 184 are provided in the substrate 165A between neighboringcell strings 170. An insulative second capping layer 181 is providedover the resulting structure in the memory cell region 104A. Theperipheral region 106A is not present in this embodiment, and thereforeincludes no substrate and no transistors. The peripheral region 106 ofthe first layer 110 is covered by the application of the secondinterlayer dielectric layer 190 that covers the memory cell region 104Aof the second layer 115.

As in the above embodiments, the substrate 165A of the second layer 115is isolated from elements of the underlying first layer 110 by the firstinterlayer dielectric layer 150. Also, as above, in the embodimentshown, the memory cell region 104A of the second layer 115 is generallyaligned with the memory cell region 104 of the first layer 110.

In the memory cell region 104A of the second layer 115, the cell strings170 are positioned on the substrate 165A in a single well 119 thatdefines an active region of the second layer 115. The substrate 165A ofthe second layer 115 can be formed, for example, of an SOI-typesubstrate, foamed, for example, using selective epitaxial growth (SEG)or laser-induced epitaxial growth (LEG), or otherwise can be appliedusing a wafer-bonding process. In an example where the material of thesubstrate 165A is n-type, the single well 119 can be p-type. In anexample embodiment for forming the single well 119, the single well 119can be formed by applying a dopant to an upper region of the substrate165A surface, and the dopant is then diffused into the body of thesubstrate 165A using a high-temperature application. As a result, thehighest concentration of impurities is at a bottom portion of the singlewell 119.

Continuing to refer to FIG. 5A, contacts for common source lines (CSL)are next formed in a manner similar to that described above inconnection with FIG. 2D. Contact holes 303 are foamed in the second andfirst layers 115, 110 of the resulting structure to contact theunderlying source regions 130, 180 of the cell strings 120, 170 of thefirst layer 110 and second layer 115 respectively. The contact holes 303are formed so as to be isolated from other elements of the first andsecond layers 110, 115. The contact holes 303 are then filled with aconductive material to provide common source line contacts 301 thatprovide electrical contact with the source regions 130, 180.

Referring to FIG. 5B, contacts for bit lines are formed in a mannersimilar to that described above in connection with FIG. 2E. A thirdinterlayer dielectric layer 195 is provided over the resultingstructure. Bit line holes 305 are formed in the second and first layers115, 110 of the resulting structure to contact the underlying commondrain regions 134, 184 of the cell strings 120, 170 of the first layer110 and second layer 115 respectively. The bit line holes 305 are formedso as to be isolated from other elements of the first and second layers110, 115. The bit line holes 305 are then filled with a conductivematerial for providing bit line plugs 307 that provide electricalcontact with the common drain regions 134, 184. At this time, peripheraltransistor contact holes 200 can also be formed through the third,second and first interlayer dielectric layers 195, 190, 150 in theperipheral region of the device, and plugs applied to form peripheralcontacts 210 that contact the source, drain and/or gate elements 140,142 of the peripheral transistors of the first layer 110.

Referring to FIG. 5C, bit lines are formed in a manner similar to thatdescribed above in connection with FIG. 2F. Bit lines 220 are formed andpatterned on the resulting structure to connect the common drain regions134, 184 of the cell strings 120, 170 of the first and/or second layers110, 115 of the device. At the same time, other types of interconnectvias 222 can be formed in the peripheral region 106A and in the memorycell region 104A. A fourth interlayer dielectric layer 230 is optionallyprovided over the resulting structure to insulate the bit lines 220 andinterconnect vias 222.

In the resulting multiple-layered semiconductor device, the substrate165A of the second layer 115 is physically and electrically isolatedfrom the peripheral transistors 140 of the first layer 110 by virtue ofthe fact that they lie on different substrates. As a result, theoperation of the cell strings 170 of the second layer 115 is physicallyand electrically isolated from the peripheral transistors 140 of thefirst layer 110. Thus, during a programming or erase operation of thememory cells 176 of the second layer 115, requiring a high voltage to beapplied to the single well 119 in the substrate 160 of the second layer115, the high voltage will not interfere with the operation of theperipheral transistors 140 of the first layer 110, since they arephysically and electrically isolated from each other. Therefore, amultiple well configuration is not required in the second layer 115. Asa result, the substrate 165A of the second layer 115 can be prepared tohave a thinner profile, and with fewer processing steps, resulting indevices with higher-density, greater reliability, and reducedfabrication costs.

At the same time, since the memory cells 126 of the first layer 110 areformed in the multiple-well structure of the memory cell region 104A ofthe first substrate 100, including the pocket well 116 and deep well114, and since the peripheral transistors 140 of the first layer areformed in the peripheral well 118 of the peripheral region 106A of thefirst substrate 100, they too are isolated from each other, as a resultof the triple-well configuration of the first layer 110. Therefore,during a programming or erase operation of the memory cells 126 of thefirst layer 110, requiring a high voltage to be applied to the pocketwell 116, the high voltage will not interfere with the operation of theperipheral transistors 140 in the peripheral region 106A of the firstlayer 110, since they are isolated from each other. In the embodiment ofFIGS. 5A-5C, it is not necessary to form the peripheral region of thesecond layer 115, and only the memory cell region 104A of the secondlayer 115 is applied to the first layer 110. This reduces the number ofprocessing steps required for fabricating the device, reducingmanufacturing costs.

In the present example, since the common source line contact plugs 301make direct contact with the source regions 180 of the second layer 115and inner regions of the second substrate 165A, and since the bit lineplugs 307 make direct contact with the common drain regions 184 andinner regions of the second substrate 165A, they are formed, forexample, of n+ type doped polysilicon, assuming a p+ type secondsubstrate 165A. On the other hand, the contact plugs 192, 194, 197, 198of the embodiments of FIG. 2A-2F can be formed of metal, for exampletungsten, since the contact plugs 192, 194, 197, 199 are physicallyisolated from the second substrate 165A or do not otherwise pass throughthe second substrate 165A

FIG. 6 is a block diagram of a memory card that includes a semiconductordevice in accordance with the embodiments of the present invention. Thememory card 1200 includes a memory controller 1220 that generatescommand and address signals C/A and a memory module 1210 for example,flash memory 1210 that includes one or a plurality of flash memorydevices. The memory controller 1220 includes a host interface 1223 thattransmits and receives command and address signals to and from a host, acontroller 1224, and a memory interface 1225 that in turn transmits andreceives the command and address signals to and from the memory module1210. The host interface 1223, the controller 1224 and memory interface1225 communicate with controller memory 1221 and processor 1222 via acommon bus.

The memory module 1210 receives the command and address signals C/A fromthe memory controller 1220, and, in response, stores and retrieves dataDATA I/O to and from at least one of the memory devices on the memorymodule 1210. Each memory device includes a plurality of addressablememory cells and a decoder that receives the receives the command andaddress signals, and that generates a row signal and a column signal foraccessing at least one of the addressable memory cells duringprogramming and read operations.

Each of the components of the memory card 1200, including the memorycontroller 1220, electronics 1221, 1222, 1223, 1224, and 1225 includedon the memory controller 1220 and the memory module 1210 can employmultiple-layered semiconductor memory devices of the type disclosedherein.

FIG. 7 is a block diagram of a memory system 1300 that employs a memorymodule 1310, for example, of the type described herein. The memorysystem 1300 includes a processor 1330, random access memory 1340, a userinterface 1350 and a modem 1320 that communicate via a common bus 1360.The devices on the bus 1360 transmit signals to and receive signals fromthe memory card 1310 via the bus 1360. Each of the components of thememory system 1300, including the processor 1330, random access memory1340, user interface 1350 and modem 1320 along with the memory card 1310can employ vertically oriented memory devices of the type disclosedherein. The memory system 1300 can find application in any of a numberof electronic applications, for example, those found in consumerelectronic devices such as solid state disks (SSD), camera image sensors(CIS) and computer application chip sets.

The memory systems and devices disclosed herein can be packaged in anyof a number of device package types, including, but not limited to, ballgrid arrays (BGA), chip scale packages (CSP), plastic leaded chipcarrier (PLCC) plastic dual in-line package (PDIP), multi-chip package(MCP), wafer-level fabricated package (WFP), and wafer-level processedstock package (WSP).

While embodiments of the invention have been particularly shown anddescribed with references to preferred embodiments thereof, it will beunderstood by those skilled in the art that various changes in form anddetails may be made herein without departing from the spirit and scopeof the invention as defined by the appended claims.

1. A method of forming a multiple-layered memory device, comprising:providing a first memory device layer comprising: providing a firstsubstrate including a first memory cell region, the first substratecomprising a semiconducting material doped with impurity of a firsttype; providing a first well in an upper region of the first memory cellregion, the first well comprising a semiconducting material doped withimpurity of a second type opposite the first type; and providing asecond well in the first well, the second well comprising asemiconducting material doped with impurity of the first type, thesecond well of defining a first active region of the first substrate;and providing multiple first cell strings arranged on the firstsubstrate in the first active region; and providing a second memorydevice layer on the first memory device layer comprising: providing asecond substrate including a second memory cell region, the secondsubstrate including only a single well in the second memory cell region,the single well of the second memory cell region comprising asemiconducting material doped with impurity of one of the first type andsecond type, the single well defining a second active region in thesecond memory cell region of the second substrate; and providingmultiple second cell strings arranged on the second substrate in thesecond active region.
 2. The method of claim 1 further comprisingproviding an interlayer dielectric layer on the first memory devicelayer between the first memory device layer and the second memory devicelayer.
 3. The method of claim 1 wherein the first type of impurity isn-type and wherein the second type of impurity is p-type.
 4. The methodof claim 1 wherein the first type of impurity is p-type and wherein thesecond type of impurity is n-type.
 5. The method of claim 1 wherein thesemiconducting material of the single well of the second substrate isdoped with impurity of the first type.
 6. The method of claim 1 whereinat least one of the first and second memory device layers furtherincludes a peripheral region.
 7. The method of claim 6 wherein providingthe first memory device layer further comprises providing a firstperipheral region including first peripheral transistors on the firstsubstrate.
 8. The method of claim 7 further comprising removing aportion of the second substrate that lies on the first peripheral regionof the first substrate.
 9. The method of claim 7 wherein the secondsubstrate of the second memory device layer is constructed and arrangedso that when the second substrate is provided on the first substrate, noportion of the second substrate lies on the first peripheral region ofthe first substrate.
 10. The method of claim 6 wherein providing thesecond memory device layer further comprises providing a secondperipheral region including second peripheral transistors on the secondsubstrate.
 11. The method of claim 10 further comprising physicallyisolating a portion of the second substrate of the second peripheralregion of the second memory device layer from a portion of the secondsubstrate of the second memory cell region, including the second cellstrings.